The present invention relates generally to an electric discharge machining method and an apparatus, and more particularly to such a method and apparatus for machining, by means of the electric discharge, a microshaft such as microelectrode employed for forming a microhole such as a nozzle of an ink jet printer and an optical fiber connector.
One prior method of machining a micro or fine shaft through the electric discharge technique is known, as exemplified by description in "National Technical Report" Vol. 31 No. 5 Page 105, in which a microelectrode is electrically discharged with respect to a metallic block so that its diameter is gradually decreased to a desirable value. One important problem in such a conventional electric discharge machining method is, however, to scattering in diameters of the machined microelectrodes due to wearing of the metallic block during the electric discharge process. This results in difficulty being encountered to accurately machine the microelectrodes so as to have the desirable diameter. Furthermore, in the case that the microelectrode is machined so as to have a considerably small diameter, the microelectrode tends to be deflected during the electric discharge process to cause the microelectrode to be finished to a tapered configuration.